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  1. JDK
  2. JDK-8148854

Class names "SomeClass" and "LSomeClass;" treated by JVM as an equivalent

    Details

    • Subcomponent:
    • Resolved In Build:
      b137
    • CPU:
      x86_64
    • OS:
      windows_7

      Backports

        Description

        FULL PRODUCT VERSION :
        java version "1.8.0_65"
        Java(TM) SE Runtime Environment (build 1.8.0_65-b17)
        Java HotSpot(TM) 64-Bit Server VM (build 25.65-b01, mixed mode)


        FULL OS VERSION :
        Microsoft Windows [Version 6.1.7601]

        A DESCRIPTION OF THE PROBLEM :
        Constant pool entries of type "class" with class name "LClassName;" (without quotes) are interpreted by JVM as a reference to the class "ClassName".

        Here is an excerpt from constant pool as reported by javap:

          #15 = Utf8 LBadHelloWorld;
          #16 = Class #15 // "LBadHelloWorld;"

        The bytecode instruction

                 0: new #16 // class "LBadHelloWorld;"

        will actually instantiate class with name "BadHelloWorld".

        THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Yes

        THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Yes

        STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
        Compile and run generator class that will generate problematic *.class file.
        See "Source code for an executable test case" field below for generator source.

        EXPECTED VERSUS ACTUAL BEHAVIOR :
        Expected:
         - Some kind of verification and/or runtime error, probably "NoClassDefFoundError".

        Actual:
         - Generated sample class file run without any visible problems.
        REPRODUCIBILITY :
        This bug can be reproduced always.

        ---------- BEGIN SOURCE ----------
        //
        // !!! The ASM 5.x (http://asm.ow2.org/) library MUST be available in class path to compile and run the following code!
        //

        import java.util.*;
        import java.io.OutputStream;
        import java.nio.file.Files;
        import java.nio.file.Paths;

        import org.objectweb.asm.*;

        public class HelloWorldGen implements Opcodes {

            public static String GENERATED_CLASS_NAME = "BadHelloWorld";

        public static byte[] dump () throws Exception {

        ClassWriter cw = new ClassWriter(0);
        FieldVisitor fv;
        MethodVisitor mv;
        AnnotationVisitor av0;

        cw.visit(52, ACC_PUBLIC + ACC_SUPER, GENERATED_CLASS_NAME, null, "java/lang/Object", null);

        {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
        mv.visitInsn(RETURN);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
        }
        {
        mv = cw.visitMethod(ACC_PUBLIC, "toString", "()Ljava/lang/String;", null, null);
        mv.visitCode();
        mv.visitLdcInsn("Hello, world!");
        mv.visitInsn(ARETURN);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
        }
        {
        mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC + ACC_VARARGS, "main", "([Ljava/lang/String;)V", null, null);
        mv.visitCode();
        mv.visitTypeInsn(NEW, "L" + GENERATED_CLASS_NAME + ";");
        mv.visitInsn(DUP);
        mv.visitMethodInsn(INVOKESPECIAL, "L" + GENERATED_CLASS_NAME + ";", "<init>", "()V", false);
        mv.visitVarInsn(ASTORE, 1);
        mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitVarInsn(ALOAD, 1);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/Object;)V", false);
        mv.visitInsn(RETURN);
        mv.visitMaxs(2, 2);
        mv.visitEnd();
        }
        cw.visitEnd();

        return cw.toByteArray();
        }

            public static void main(String... args) throws Exception {
                try (OutputStream out = Files.newOutputStream(Paths.get(GENERATED_CLASS_NAME + ".class"));) {
                    out.write(dump());
                }
            }

        }

        ---------- END SOURCE ----------

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                • Assignee:
                  rprotacio Rachel Protacio (Inactive)
                  Reporter:
                  webbuggrp Webbug Group
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                  • Created:
                    Updated:
                    Resolved: